Write a program that takes a key (a number from 1 to 26) an input file name, and an output file name from the command line and uses the key to encrypt it with a Caesar cipher. A Caesar cipher performs modular addition of the key and the letter. If the key is 1 then a->b, b->c, ..., y->z, z->a . Ignore all the things that arent the letters from a to z (simply pass them through) and you will want to put the letters into lower case. Use the file message1.txt and a key of 7 to encrypt it. (You can do this one pretty easily in bash too.)

PLEASE ANSWER ONLY IN BASH/LINUX